Sample cell for liquid scintillation counters

ABSTRACT

A sample cell is disclosed for adapting liquid scintillation counters to chemiluminescence measurements. A glass reaction vessel is secured within a support tube of substantially the same size and shape as the elevator passageway of a liquid scintillation counter. An O-ring seals the passageway against ambient light when the reaction vessel is in the counting position. A plurality of glass tubes are sealed within the vessel and are brought through the top of the support tube by black polyethylene tubing, the black polyethylene preventing light piping from the exterior to within the reaction vessel. Two of the glass tubes are open and terminate near the bottom of the vessel to fill and empty the vessel. A third is sealed at its lower end and receives a thermistor to measure sample temperature. Two other tubes are interconnected by a tubular helix for circulation of a thermostating fluid. The vessel may be sandblasted and the bottom silvered or aluminized to improve optical transmission characteristics. The bottom is covered with felt to absorb mechanical shock.

United States atet [191 Neary SAIVWLE CELL FOR LIQUID SCINTILLATIONCOUNTERS Inventor: Michael P. Neary, Newport Beach,

Calif.

Beckman Instruments, Inc., Fullerton, Calif.

Assignee:

Filed: Nov. 27, 1970 Appl. No.: 93,254

References Cited UNITED STATES PATENTS 7/l970 Webb ..195/l03.5 R

4/ 1969 Packard ..250/ 106 SC 12/1967 Hoffman ..l95/l03.5 R

[4 1 Apr. 10, 1973 Primary Examiner-James W. Lawrence AssistantExaminerDavis L. Willis Attorney-Paul R. Harder and Robert J. Steinmeyer[57] ABSTRACT A sample cell is disclosed for adapting liquidscintillation counters to chemiluminescence measurements. A glassreaction vessel is secured within a support tube of substantially thesame size and shape as the elevator passageway of a liquid scintillationcounter. An O-ring seals the passageway against ambient light when thereaction vessel is in the counting position. A plurality of glass tubesare sealed within the vessel and are brought through the top of thesupport tube by black polyethylene tubing, the black polyethylenepreventing light piping from the exterior to within the reaction vessel.Two of the glass tubes are open and terminate near the bottom of thevessel to fill and empty the vessel. A third is sealed at its lower endand receives a thermistor to measure sample temperature. Two other tubesare interconnected by a tubular helix for circulation of a thermostatingfluid. The vessel may be sandblasted and the bottom silvered oraluminized to improve optical transmission characteristics. The bottomis covered with felt to absorb mechanical shock.

10 Claims, 1 Drawing Figure PATENTED APRI 01575 INVENTOR. MICHAEL P.NEARY BY W ATTORNEY SAMPLE CELL FOR LIQUID SCINTKLLATION COUNTERS Thisinvention relates generally to the field of chemiluminescencemeasurements and more particularly to an in situ sample cell for use inliquid scintillation counters to adapt the counter for chemiluminescentmeasurements.

Certain chemical reactions result in the production of molecules in anexcited electronic state and as these molecules dissipate energy inreturning to the ground state photons or small flashes of light areemitted. Certain other chemical reactions, while not chemiluminescent inand of themselves, are capable of transferring energy to an emitter orfluorescer which, upon receipt of the energy from the reaction, producesphotons. By counting these photons or light flashes, usually as afunction of time, various quantitative and qualitative determinationsconcerning the reaction may be made.

Liquid scintillation counters have been employed to count the photons oflight emitted by a scintillator or fluor which is the result ofexcitation of the scintillator by radioactive particles. Most modernliquid scintillation counters utilize a pair of diametrically opposedphotomultiplier tubes facing onto a light tight counting chamber.Although capable of counting the photons emitted from chemiluminescentreactions these modern liquid scintillation counters do not provide aconvenient means for such counting since it is the general practice tomix the scintillator with the radioactive material outside the countingchamber, place the sample in a vial and lower the vial into the countingchamber by an elevator through a double light tight sealing mechanismarranged such that the counting chamber at all times is sealed againstambient light. This mechanism is not ideally suited to the measurementof chemiluminescent reactions since it is generally desired to registerthe photon emission data from time zero when the reactants are mixed tocompletion or for some predetermined period of time. The time taken tolower the mixed reactants from outside the counting chamber through thedouble light seal and into the counting chamber results in loss ofsignificant photoemission data.

In my copending application Ser. No. 93,253 entitled Demountable SampleCell Holder and Cell for Liquid Scintillation Counters, filed on evendate herewith and assigned to the assignee of the instant invention,there is disclosed a sample cell holder for adapting liquidscintillation counters for chemiluminescent mea surements. This sampleholder and cell allows the in situ mixing of the reactants within thecounting chamber such that the photons may be counted from time zero.The sample cell holder and cell disclosed in the referenced applicationis mounted within one of the photomultiplier apertures in the countingchamber. This requires the researcher to remove one of thephotomultiplier tubes and substitute the cell holder disclosed therein.While there are advantages to the cell holder and cell disclosed in theaforementioned application as well as in the measurement techniqueutilizing only a single photomultiplier tube, under some circumstancesthe researcher may desire to utilize both photomultiplier tubes, whichin most modern instruments allows coincidence gating, or maynot desireto modify the liquid scintillation counter to the extent necessary toutilize the cell holder and cell disclosed in the aforementionedapplication.

It is, therefore, the principal object of this invention to provide asample cell for liquid scintillation counters to adapt these counters tothe measurement of chemiluminescent reactions and which does not requirethe modification of the liquid scintillation counter.

Another object of the present invention is to provide a sample cell forliquid scintillation counters which allows in situ mixing of thereactants from which the photons are derived within the counting chamberthus allowing measurement of the photoemission data from the time thereactants are mixed.

Other objects and many of the attendant advantages of this inventionwill become more readily apparent as the same becomes better understoodby reference to the following detailed description when read inconnection with the accompanying drawing and in which:

The single FIGURE is a partial cross-sectional view of a modern liquidscintillation counter with a sample cell constructed in accordance withthe teachings of this invention in the counting position.

Referring now to the drawing there is illustrated a partial sectionalview of the counting chamber 10 which is typically formed within a heavycasting ll of any suitable material such as brass. Access to thecounting chamber from the outer surface 12 of the counter is normallythrough an elevator passageway 13. Also illustrated schematically is thesample vial elevator 14 in the counting position, it being understoodthat the elevator passageway has a light sealing shutter at the topthereof (not shown) and the elevator being arranged such that as itrises, a light seal is made at the junction of the elevator passagewayand the counting chamber or within the elevator passageway prior toopening of the outer light sealing shutter so that the chamber 10 is atall times sealed against ambient light. Since the elevator is maintainedin its counting position and the outer shutter is opened at all timeswhile utilizing the invention, the elevator, its light sealing mechanismand the shutter have not been shown in detail and form no part of thisinvention.

In most modern liquid scintillation counters a pair of photomultipliertubes 15 are arranged about the counting chamber in diametricallyopposed positions and are retained within the apertures in casting 11 bypairs of O-rings 16 which seal the counting chamber against ambientlight.

In order to adapt the liquid scintillation counter to photon countingand to commence the counting at time zero when the reactants are mixedit is necessary to provide a sample cell capable of in situ mixing ofthe reactants. For this purpose there is provided a sample cell orreaction vessel 18 formed of any suitable light transmitting materialsuch as glass or quartz. The sample cell 18 has a bottom portion 19 anda top portion 20, it being preferred to integrally form the top andbottom portions with the side walls. Sealed within the top portion 20 ofthe sample cell 18 are a pair of conduits 22 which extend from outsidethe reaction vessel to just above the bottom portion 19, it beingpreferred to terminate these conduits as close to the bottom wall aspossible without unduly restricting the flow of fluid therethrough. Athird tube 23 also extends from the upper outer portion of the vessel toapproximately twothirds the distance toward the bottom of the vessel andis closed at its lower end. A thermistor 24 may be contained within thetube 23 to measure the temperature of the reactants if desired.

In certain reactions it may be desirable to control the temperature ofthe reactants or to program their temperature as a function of time. Forthis purpose there may be, if desired, provided within the reactionvessel a tubular helix 26 having an inlet and outlet conduit 27 and 28extending beyond and fused into the top portion 20 of the sample cell18.

The reaction vessel or sample cell 18 is secured to a support tube 30 byan epoxy resin collar 31, the diameter of the reaction vessel beingreduced slightly in size near its upper end to fit within the supporttube 30 and to provide space therebetween for the epoxy resin collar. Ofcourse, any other suitable material may be utilized to secure thesupport tube 30 and the reaction vessel 18. The support tube ispreferably of rigid material such as aluminum, is closed at its upperend and has a plurality of apertures in the upper end thereof for the 1purpose of bringing the connecting tubes 33 to the exterior of theassembly. The connecting tubes 33 connect to respective ones of thetubing or conduits within the reaction vessel and is preferably of blackpolyethylene, bent at a right angle at the exterior to prevent any lightpiping from outside the instrument. The tubing connected to tube 23allows the lead wires of thermistor 24 to be brought to the exterior ofthe cell assembly, the tubing connected to conduits 22 allowintroduction and removal of the reactants to the cell and the tubingconnected to conduits 27 and 28 allows circulation of a thermostattingfluid within the glass helix. The junction of the tubing 33 and thesupport tube 30 where the tubing 33 passes through the apertures issealed against the passage of ambient light. Black rubber grommets suchas neoprene have been found suitable for constructing this seal.

A pair of annular grooves are preferably provided in the exterior ofsupport tube 30 for receiving a pair of O-rings 35. The support tube isof substantially the same size and shape as the elevator passageway andas the reaction vessel is introduced into the passageway, O-rings 35mate with the elevator passageway to seal the passageway against ambientlight.

As is well known, most modern liquid scintillation instruments have alight sealing shutter at the outer surface which cooperates with theseal associated with the elevator shaft such that the counting chamber10 is at all times sealed against ambient light. By placing the lowerO-ring 35 at a position closely adjacent the lower end of support tube30 it is possible to raise the elevator just sufficiently to seal thelower end of the elevator passageway at the entrance into the countingchamber, open the light sealing shutter at the top and insert the samplecell assembly into the elevator passageway until the lower O-ring sealsthe upper portion of the passageway against ambient light. The elevatorcan then be lowered to the counting position and the sample cellassembly pushed down the elevator passageway until the reaction vessel18 is in the counting position. In this manner the high voltage to thephotomultiplier tubes need not be removed during insertion and removalof the sample cell.

Returning again to the reaction vessel or sample cell 18 the outersurface of the bottom wall portion 19 is provided with a silvered oraluminized coating 36 to enhance transmission. If desired the bottom mayalso be covered with felt 37 to provide mechanical protection. Ifdesired, the exterior of the sample cell may be sandblasted to improveits light transmission characteristics.

In operation, after positioning the sample cell assembly in the countingposition one of the reactants is added to the reaction vessel throughone of the inlet tubes. The other reactant is then added, it beinggenerally preferable to add the second reactant through the other tubeto avoid contact with the residue of the other prior to entry into thereaction vessel. If the temperature of the reactants is to be measured athermistor is slipped into the central tube 23 prior to introducing thereactants. if the reaction is to be thermostatted, a thermostattingfluid is circulated through the helix 26 via the inlet and outletconduits 27 and 28. After the measurement, the reactants are pumped fromthe cell by any suitable means, the cell being then washed with anysuitable material which will I not contaminate or inhibit the subsequentreaction to be measured. The inlet and outlet conduits are brought asclosely to the bottom of the reaction vessel as possible withoutsubstantially inhibiting the flow of fluid therethrough. All of thetubes and conduits within the reaction vessel, are constructed ofmaterial which permit good transmission of photons and are generallypreferably constructed of glass or quartz.

The geometry of the reaction vessel may, of course, be changed as wellas the geometry of the support tube to fit the particular instrumentbeing utilized although most modern instruments utilize a circularelevator passageway. The sample cell assembly disclosed provides for themeasurement of chemiluminescent reactions with greater reproducibilityand ease owing generally to the in situ nature of the sample mixing. Thedata thus obtained will be of inherently better quality than has beenheretofore possible since measurements can take place immediately uponmixture of the reactants.

Although the sample cell assembly has been described in connection withthe preferred embodiment it is obvious that other embodiments andarrangements of parts are possible without departing from the inventionas defined by the appended claims.

What is claimed is:

1. A sample cell for use in a liquid scintillation counter having alight tight counting chamber and an elevator passageway extending fromthe exterior of said counter into said chamber comprising:

a cell body of material transparent to photons;

a plurality of tubes extending from outside said cell body into theinterior thereof, at least one of said tubes being open at each endthereof to allow sample fluid to pass therethrough;

a support tube secured to one end of said cell body, said support tubebeing of substantially the same size and shape as said elevatorpassageway and of sufficient length to extend beyond said passagewaywhen said cell body is within said counting chamber; and

means on said support tube for cooperating with said passageway forsealing said counting chamber against ambient light when said cell bodyis in said counting chamber.

2. The sample cell according to claim 1 wherein each of said pluralityof tubes extend through that portion of said support means extendingbeyond said passageway, at least that portion of said tubes extendingthrough said support tube being of black inert material.

3. The sample cell according to claim 2 wherein one of said plurality oftubes is closed at the end within said cell body. 1 r

4. The sample cell according to claim 3 wherein two of said tubes areopen at each end thereof to allow sample fluid flow therethrough, eachof said open tubes extending substantially to the bottom of said cellbody.

5. The sample cell according to claim 4 further including tube meanswithin said cell body interconnecting a pair of said plurality of tubesfor circulating a thermostatting fluid therethrough.

6. A sample cell for use in a liquid scintillation counter having alight tight counting chamber and an elevator passageway extending fromthe exterior of said counter into said chamber comprising:

a glass reaction cell;

a plurality of glass tubes sealed in one end of said cell, at least apair of said tubes being opened at both ends and extending substantiallyto the other end of said cell;

a support tube secured to said one end of said cell, said support tubebeing completely closed and of substantially the same size, and shape assaid elevator passageway, said support tube being longer than saidelevator passageway and extended therefrom when said cell is in thecounting chamber;

at least one O-ring on the outer surface of said support tube, saidO-ring fitting against the wall of said passageway to seal saidpassageway against ambient light when said cell is in the countingchamber;

black inert tubing means connected to each of said glass tubes andextending through the portion of said support tube extending beyond saidpassageway.

7. The sample cell according to claim 6 wherein one of said glass tubesis sealed at its end within said cell; and

a thermistor is said last named tube for measuring the temperature ofsample in said cell.

8. The sample cell according to claim 7 wherein the outer surface of theother end of said cell is coated with a reflective material; and

a shock resistant material secured over said coating.

9. The sample cell according to claim 7 wherein the outer surface ofsaid cell has been sandblasted.

10. The sample cell according to claim 9 further including:

glass tubing means in the form of a helix within said cell andinterconnecting two of said glass tubes for circulating a thermostattingfluid therethrough.

1. A sample cell for use in a liquid scintillation counter having alight tight counting chamber and an elevator passageway extending fromthe exterior of said counter into said chamber comprising: a cell bodyof material transparent to photons; a plurality of tubes extending fromoutside said cell body into the interior thereof, at least one of saidtubes being open at each end thereof to allow sample fluid to passtherethrough; a support tube secured to one end of said cell body, saidsupport tube being of substantially the same size and shape as saidelevator passageway and of sufficient length to extend beyond saidpassageway when said cell body is within said counting chamber; andmeans on said support tube for cooperating with said passageway forsealing said counting chamber against ambient light when said cell bodyis in said counting chamber.
 2. The sample cell according to claim 1wherein each of said plurality of tubes extend through that portion ofsaid support means extending beyond said passageway, at least thatportion of said tubes extending through said support tube being of blackinert material.
 3. The sample cell according to claim 2 wherein one ofsaid plurality of tubes is closed at the end within said cell body. 4.The sample cell according to claim 3 wherein two of said tubes are openat each end thereof to allow sample fluid flow therethrough, each ofsaid open tubes extending substantially to the bottom of said cell body.5. The sample cell according to claim 4 further including tube meanswithin said cell body interconnecting a pair of said plurality of tubesfor circulating a thermostatting fluid therethrough.
 6. A sample cellfor use in a liquid scintillation counter having a light tight countingchamber and an elevator passageway extending from the exterior of saidcounter into said chamber comprising: a glass reaction cell; a pluralityof glass tubes sealed in one end of said cell, at least a pair of saidtubes being opened at both ends and extending substantially to the otherend of said cell; a support tube secured to said one end of said cell,said support tube being completely closed and of substantially the samesize, and shape as said elevator passageway, said support tube beinglonger than said elevator passageway and extended therefrom when saidcell is in the counting chamber; at least one O-ring on the outersurface of said support tube, said O-ring fitting against the wall ofsaid passageway to seal said passageway against ambient light when saidcell is in the counting chamber; black inert tubing means connected toeach of said glass tubes and extending through the portion of saidsupport tube extending beyond said passageway.
 7. The sample cellaccording to claim 6 wherein one of said glass tubes is sealed at itsend within said cell; and a thermistor is said last named tube formeasuring the temperature of sample in said cell.
 8. The sample cellaccording to claim 7 wherein the outer surface of the other end of saidcell is coated with a reflective material; and a shock resistantmaterial secured over said coating.
 9. The sample cell according toclaim 7 wherein the outer surface of said cell has been sandblasted. 10.The sample cell according to claim 9 further including: glass tubingmeans in the form of a helix within said cell and interconnecting two ofsaid glass tubes for circulating a thermostatting fluid therethrough.